General Zaroff tells Rainsford, "It would be impossible for me to tell you how many aminals I have killed." He has become jaded; his appetite for killing has been satiated by hunting all types of wild game since he was five years old, slaughtering men in war.

One reason that Zaroff has become weary of hunting animals is the fact that he is such a skilled hunter that he is capable of capturing or killing his prey without challenge: "I always got my quarry. Always. There is no greater bore than perfection."

Zaroff is bored of hunting animals because the hunting has become too easy. He is no longer challenged by "unthinking beasts" and so now prefers to hunt reasoning, strategizing creatures. However, even the people he hunts bring Zaroff close to boredom...until he goes up against Rainsford.

Sadly, Zarrof gets pleasure from killing but also from the challenge involved. He wants to hunt because he feels like he can use his skills, skills that he has carefully honed over the years. Unfortunately he has gotten so good that it is no longer a challenge.

Zaroff has become bored because he has come to a point where he outthinks the wily animals that he has been pursuing. That's why he turns to humans. Only they are capable of thinking at the high level of reasoning that he does.

People like Rainsford are thrill-seekers at heart. It's true he's a hunter and likes the challenge of stalking and killing his prey, but at the heart of hunting is the thrill of the chase. He says he's bored because no one is challenging him anymore. Let's face it, the captives whom he's shipwrecked on his island are probably too scared to be much of a challenge. Hunting is as much an intellectual game, and he's already figured out how every known animal thinks. Humans think differently, of course, which is why he started hunting them. However, the others were too scared to think--they must have just run for their lives. So, he's bored.

He is bored. He is so good at hunting, that he does not have a challenge anymore and will do anything to desire a challenge, which is hwy he goes to such lengths. Animals can only react but they can't strategize and plan.

I agree with the second post by mwestwood, and would like to add a few more things:

General Zaroff uses an interesting word to describe why he prefers to hunt human beings over animals: ennui (a good SAT word), which means boredom. The general, who has succeeded in hunting the most dangerous animal quarry, is too good at hunting animals. He desires a quarry with which he can "match his wits." The disadvantage of animals is that they cannot reason, making them easy prey. General Zaroff desires more challenging targets, prey that can think.

General Zaroff tells Rainsford, "It would be impossible
for me to tell you how many aminals I have killed." He has
become jaded; his appetite for killing has been satiated by hunting
all types of wild game since he was five years old, slaughtering
men in war.

One reason that Zaroff has become weary of hunting animals
is the fact that he is such a skilled hunter that he is capable of
capturing or killing his prey without challenge: "I always
got my quarry. Always. There is no greater bore than
perfection."